Rob Taylor from Xbox World 360 Magazine is the first games writer to complete GTA IV. He, and a number of other writers, were granted special access to review the game last month. There's a short interview with him over at GamesRadar, where he discusses his thoughts on the new game. Here's an excerpt:
How many "Woooaah, Jesus that's amazing!" moments did you have?
Without giving away any spoilers; lots! I think, overall though, it'll be three overall things that entrance GTA fans like never before. The City is one, with a lighting engine that has to be seen to be believed, plus the incredible dialogue and characterisation is genuinely Oscar-worthy and Niko Bellic is absolutely the most amazing protagonist in any game I've ever played. Finally, multiplayer of course!
Link: GamesRadar: "He's finished Grand Theft Auto IV!"